Pig Myocardial Infarction Model Mri Myocardial First Pass Perfusion And De-mri And Ctni Experimental Research

Objectives:The reduce of myocardial perfusion occurs before the electrocardiogram(ECG) changes and clinical syndrome(angina),so myocardial perfusion abnormalities have a positive meaning in the diagnosis of coronary artery disease.The aim of this study is to explore the value of the first-pass myocardial perfusion MR imaging in evaluating the ischemic myocardial perfusion and viability.Especially,to investigate to perfusion curves(time-signal intensity curves) changes of the ischemic myocardium.In addition, to explore the limitations existing in the current MR first-pass perfusion imaging study.Materials and Methods:Ten porcine model with myocardial infarction had the preoperative and postoperative MR first-pass myocardial perfusion imaging examination.The perfusion reduce or defects on the MR myocardial perfusion imaging were observed. And the time-signal intensity curves in the regions with the perfusion reduce or defects and normal regions were drawed by the image post-processing software.The peak time,peak signal intensity of curve were statistical analyzed.After MRI examination,the experimental pigs were executed and its heart been had the TTC staining and pathological examination.Results:The preoperative myocardial perfusion in the all of the 10 pigs is nomal,but there is myocardial perfusion decrease and defect in 8 experimental pigs after operation.The curves in the area with perfusion defects have no obvious peak and have a sligtly increase in late time.The curves in the area around perfusion defect can be seen the peak,but the peak signal intensity is lower than normal inferior and lateral myocardial wall(P<0.05);and the peak time is delayed compared with normal inferior and lateral myocardial wall(P<0.05).There are myocardial infarction in the perfusion defects areas and its were certified by TTC staining and pathological examination.The interstitial edema and myocardial degeneration can be seen in the perfusion reduced areas.Conclusion:MRI fist-pass myocardial perfusion imaging combined with time-signal intensity curves analysis can evaluate perfusion changes of the regional myocardial microcirculation.It may be useful in assessing the ischemic myocardial viability.But there are some limitations in the the clinical application. Objectives:Delayed-enhancement MR imaging(DE-MRI) is rapidly becoming a prominent and effective means in the evaluation of myocardial viability,but there is a question about it,that is "bringt is dead"? This study aimed to explore the accuracy and question in assessment of myocardial viability by delayed-enhanced MR imaging.Materials and MethodsA total of 15 pigs were used to make the acute myocardial infarction(MI) models,and then ten successful models were underwent delayed-enhancement MR imaging at preoperation,]postoperative 24 h,72 h and 1 W,respectively.The hyperenhanced regions and segments as well as their transmural extent on DE-MRI were observed. After MR examination,2,3,5-triphenyltetrazolium chlorid(TTC) staining and pathological examination were performed.The segments with MI detected by the DE-MRI and TTC staning were made statistical analysis.Resultsâ‘ Ten MI models were made,and no abnormal signals were found on pre-operative DE-MRI.â‘¡The abnormal high signal myocardial segments were found in the all of 10 pigs after operation on delayed-enhancement MR imaging.There were a total of 30 hyperenhanced segments in ten MI models.And there was no difference in regions and segments with MI between DE-MRI and TTC staining.â‘¢In the judging transmural extent of MI,the results of DE-MRI was correlative with TTC staining(Pearson Chi-Square,P<0.05);and the concordance was good(K>0.75).But the results of two methods was different(McNemar Test,P<0.05). The transmural extent judged by DE-MRI was higher than TTC staining. â‘£24-hour pathology of high signal area in DE-MRI(myocardial infarction in TTC staining) showed eosinophilic cytoplasm of myocardial cells,homogeneous degeneration,nuclear pyknosis;72-hour pathology showed multifocal myocardial fibers dissoloved irregularly.1-week pathology showed myocardial fibers dissoloved, interstitial fibroblasts and capillary proliferation,small blood vessels congestive.The pathology of slightly higher signal area in DE-MRI(non-infarcion in TTC staining) showed obvious interstitial edema,edema degeneration and balloon-like change of myocardial fibers.Conclusion:DE-MRI is an excellent tool for detecting the myocardial infarction.Especially,it can cleary demonstrate the suberdocardial or transmural myocardial infarction.That is very important for the clinical evaluation and treatment of the ischemic heart disease But in the clinical evaluation we should be noted that the bright areas on DE-MRI will may be "zoom" the real areas of myocardial infarction.And we should observe whether are brightness difference in high-intensity zone. Objectives:Cardiac troponin(cTnT or cTnI) is regarded as a best marker to determine the acute myocardial injury,In addition,the delayed enhancement MR imaging is becoming the new gold standard in the clinical myocardial viability assessment.This study to explore whether the clinic reagent for detection of the serum cardiac troponin I(cTnI) in the human can be applicable to swine model with acute myocardial infarction;And to investigate the relationships between the cTnl peak value and the degree of myocardial infarction quantificated by delayed-enhancment MR imaging(DE-MRI) and pathological findings.Materials and Methods10 successful pig model with acute myocardial infarction were underwent cardiac troponin(cTnI) detection at preoperation,]postoperative 1 h,2 h,after 5 h, 24 h,48 h,72 hours and 1 week;and also were underwent Delayed-Enhancement MR imaging at preoperation,postoperative 24 h,72 h and 1 W,respectively.After MR examination,2,3,5-triphenyltetrazolium chlorid(TTC) staining and immunohistochemistry examination were performed.The degree of myocardial infarction was assessed by DE-MRI and TTC.The cTnI value of 24h after the operation and the degree of myocardial infarction were made correlation analysis.Resultsâ‘ The cardiac troponin can be seen raise at 1h after operation,and reached the peak at 24h arfter aperation,then decrease gradually.1 week later the cTnI value return to preoperative levels. â‘¡The segments of myocardial infarction were found in the all of 10 pigs on the immunohistochemistry examination.It displayed:24h group showed HHF35, Myoglobin,Desmin proteins significantly reduced in the infaction region,and pale staining,surrounded by normal myocardial cells with brown staining;72h group showed HHF35,Myoglobin,Desmin protein reduced than 24h group significantly, showed a large region with dyeing missing in the infarction region,and had the clear boundaries with the normal stained brown myocardium,1w group had no significant change compared with 72h group.â‘¢The cTnI peak values of 24h was correlated strongly to the degree of myocardial infarction assessed by TTC(correlation coefficient=0.85,P=0.002) as well as to DE-MRI(correlation coefficient =0.84,P=0.002).The scatter plot shows a clear linear correlation between the cTnI peak values and the degree of myocardial infarction assessed by TTC and DE-MRI.Conclusion:The clinical reagent for detection of the serum cardiac troponin I(cTnI) can be applicable to swine model.The cTnI measurement,specially 24h after the operation, can reflects degree of myocardial injury.DE-MRI is currently a very effective, non-invasive technique,and has high spatial resolution in detection of myocardial viability.The cTnI combined with DE-MRI will be more help for clinical work and research in coronary heart disease.